Holographic universe is it real

[wolram]

I am not a proponent of holographic principle, I believe the universe is infinite, one will start off and not come back to the same starting point , my question is how popular is the holographic principle? and why?
Not that my views mean any thing.

https://www.sciencedaily.com/releases/2017/01/170130083231.htmA UK, Canadian and Italian study has provided what researchers believe is the first observational evidence that our universe could be a vast and complex hologram. Theoretical physicists and astrophysicists, investigating irregularities in the cosmic microwave background (the 'afterglow' of the Big Bang), have found there is substantial evidence supporting a holographic explanation of the universe -- in fact, as much as there is for the traditional explanation of these irregularities using the theory of cosmic inflation.

Thank you in advance.

 

[phinds]

Personally, I think it's nonsense. Susskind, who is a big believer, has forgotten more physics than I'll ever know, but I STILL don't believe it.

 

[haushofer]

In cosmology we consider de Sitter backgrounds. It is, as I understand it, far from clear that holography can be applied to these backgrounds. But holography itself is just a mathematical conjecture, and there are good reasons to believe it is "real". To which extent, that is the real question.

 

[Grinkle]

To which extent, that is the real question.

In what ways might a holographic model be different from a non-holographic model? I thought they were alternative approaches to describing the same 3-space, and either approach is valid.

 

[wolram]

In what ways might a holographic model be different from a non-holographic model? I thought they were alternative approaches to describing the same 3-space, and either approach is valid.

Hi Grinle, I do not know how a 2d space can be the same as a 3d space, may be you can clue me in.

 

[Grinkle]

I do not know how a 2d space can be the same as a 3d space

My understanding is that the information content is the same in either representation. That is why I thought they are alternative approaches to describing the same observable universe.

A 2-d spherical surface is obviously different than a 3-d volume. Perhaps mistakenly, I wasn't taking the holographic principle to literally be saying that the only 'real' stuff in the universe is physically located on a 2-d spherical surface.

 

[Greg Bernhardt]

Saw this story on USA Today of all places. More pop sci getting ahead of itself?

 

[fresh_42]

Well, there is still this true statement from @phinds

Susskind, who is a big believer, has forgotten more physics than I'll ever know

which is probably true for many of us. I always have to think about Stokes if it comes to the holographic principle. I searched the internet therefore as I saw this thread, and apparently I'm not the first one with this thought. Most think that this would be a bit too far fetched, but it doesn't convince me. Maybe it's really this underlying principle, that the borders contain the answers.

 

[PeterDonis]

My understanding is that the information content is the same in either representation.

That's the basic idea, yes. But notice that that means the 3-d space cannot contain all of the information that you would "naively" expect a 3-d volume to contain--because it can't contain any more information than can be stored on its boundary. So something counterintuitive is going on no matter how you look at it.

I wasn't taking the holographic principle to literally be saying that the only 'real' stuff in the universe is physically located on a 2-d spherical surface.

That depends on whose version of the principle you look at. Some of the claims in the literature pretty much amount to this. But this is still an open area of research, so the answer to most of the interesting questions at this point is "we don't know".

 

[stoomart]

That's the basic idea, yes. But notice that that means the 3-d space cannot contain all of the information that you would "naively" expect a 3-d volume to contain--because it can't contain any more information than can be stored on its boundary. So something counterintuitive is going on no matter how you look at it.

Sorry if this is a dumb question, I'm trying to wrap my mind around this holographic principle: are you referring to the limit of information density? I'm thinking the 3d boundary only contains the information of the 3d volume for its reference frame, similar to the CMB map, an idea that doesn't seem novel; I'm sure I'm missing something here though.

 

[PeterDonis]

are you referring to the limit of information density?

I'm referring to the fact that, if the holographic principle is true, the information that can be stored in a 3-d volume scales as the area of its boundary, i.e., as the 2/3 power of the volume; whereas our "naive" expectation is that it should scale as the volume.

the 3d boundary

The boundary of a 3d volume is a 2d surface.

 

[Grinkle]

if the holographic principle is true

Taking some liberties with the B level the thread was opened with, the pop-sci reasoning I recall for arriving at the maximum information density goes like -

Associate a bit of information with a particle state, and note that when particle density is at the point where a singularity would form, maximum information density is reached and the resulting event horizon has as many plank areas as there are possible particle states of the particles in the hypothesized singularity.

Is that nonsense? If its not nonsense, it seems to me that this is an interesting relationship arising from our model of black holes, not something that that depends on the location of the particles to be correct. Its just noticing that number of plank areas on the surface of an event horizon very oddly and interestingly imo corresponds to the number of possible particle states of the particles inside the singularity.

I get that in the link @wolram put in the OP the discussion is about where the particles are and not just the accounting I am asking about.

 

[fresh_42]

As I see it, the question is not so much about nonsense, but intuition. And the holographic principle is similar counter-intuitive as space-filling curves are.

 

[PeterDonis]

the pop-sci reasoning

Is not a good source for PF discussion.

Is that nonsense?

Looks like it to me.

 

[PeterDonis]

For much better non pop-sci sources about the Bekenstein bound, which is the name for the "information density" limit under discussion (i.e., based on the area of the boundary instead of the volume), see the references here:

https://en.wikipedia.org/wiki/Bekenstein_bound

 

[Grinkle]

Thanks, Peter.

 

[wolram]

Thank you for all the replies and links guys, very interesting.

 

[1oldman2]

Noteworthy.
http://www.southampton.ac.uk/news/2017/01/holographic-universe.page
"A UK, Canadian and Italian study has provided what researchers believe is the first observational evidence that our universe could be a vast and complex hologram."

Professor Kostas Skenderis of Mathematical Sciences at the University of Southampton explains: "Imagine that everything you see, feel and hear in three dimensions (and your perception of time) in fact emanates from a flat two-dimensional field. The idea is similar to that of ordinary holograms where a three-dimensional image is encoded in a two-dimensional surface, such as in the hologram on a credit card. However, this time, the entire universe is encoded!"

 

[Chronos]

While the 2d v 3d argument is valid, you still cannot derive any useful information from a hologram without a beam from other than a point source.

 

[Mordred]

I've tried finding the arxiv on 1Oldman2 post which I find interesting without the pop media explanations. If anyone has a link to it I would be interested in studying the details under the mathematical regime.

Quite frankly any heuristic explanation of the holographic principle simply doesn't properly cover it. I look at the required dimensions under the basis of how many independant variables (degrees of freedom) is required to define a system or system state. So quite frankly I would like to see how the dimensions from 2d to 3d are defined in the above terms including the symmetry reductions to 2d. In particular the reduction of the effective degrees of freedom which the holographic principle answers this question in terms of the area of surfaces in spacetime.

If anyone has the arxiv in regards to the links in this thread I would like to examine how the degrees of freedom is treated

 

[stoomart]

I've tried finding the arxiv on 1Oldman2 post which I find interesting without the pop media explanations. If anyone has a link to it I would be interested in studying the details under the mathematical regime.

I'm pretty sure both articles are based on the same source: https://arxiv.org/abs/1607.04878

 

[eltodesukane]

It is real. Space is not was it seems. That's why the max information content of a space region is proportional to the region's area, not the region's volume.
Space is emergent, not fundamental. Space is an illusion, space volume is an illusion.
A quote from Sean Carroll: Things don't happen in "space"; they happen in Hilbert space. It's the locality of interactions that tempts us to speak otherwise.
http://www.slideshare.net/seanmcarroll/against-space

 

[Mordred]

Thanks Stoomart. It will take some time to study

 

[rrogers]

I'm interested in how this differs from a "Green's function" where the boundary conditions and evolutionary rules allow you to calculate interior values.